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-   -   The definitive aeration/oxygenation experiment (http://www.homebrewtalk.com/f13/definitive-aeration-oxygenation-experiment-20832/)

Bobby_M 01-29-2007 04:11 PM

The definitive aeration/oxygenation experiment
 
Ok, so you can trust my science or not, but the results of this test will determine whether I continue to pump pure O2 into my wort from now on.

First, the setup:

2 gallon batch boiled down to a final volume of 1.75g.

2.42 pounds of Pale LME (someone gave me a Mr Beer refill kit so I had to do something with it.)

Boiled bottled water and threw in 1/2oz Cascade and let it go for 30 mins.

Added LME and let that boil for 10 minutes. (in the meantime, rehydrated half a pack of Safale S-04 dry yeast in 80dF water)

With 5 minutes left in a 45 minute boil, I threw in another 1/2oz Cascade.

Cooled with an icebath to 75dF then gently poured the wort through a straining funnel into 3 one-gallon fermenters to which I added exactly 2 tablespoons of suspended yeast. The OG was 1.050 exactly. Each fermenter got the following "aeration" activity after pitching:

#1 No deliberate aeration. It foamed a little from falling through the funnel.

#2 Capped the fermenter and shook it vigorously for exactly 2 minutes.

#3 Ran O2 through an aquarium stone for exactly 2 minutes (which was the point at which the foam was about to rise out of the neck of the fermenter.)

After the above, I rubberbanded a santized latex glove on top of the fermenters to act as a visual indicator of fermentation. The test involves a timelapse camera so an airlock would not show fermentation properly.

I set up the fermenters in front of my webcam and had it take an image every 10 seconds. I have some preliminary results that I found really interesting but I'll wait to share them when I can post the video later tonight. Hope it helps some of you make decisions. Stay tuned.

Bobby_M 01-29-2007 05:09 PM

Now, before I post results, I'd like to discuss a few things.

1. What do you expect the lag time characteristics to be for each?

2. Which should have the lowest OG after 24 hours in the fermenter?

3. Are there any aspects of my methods that may tarnish the results that I just haven't thought of? The only one I've recognized is that a 45 minute boil may not have fully depleted the disolved oxygen. I should have boiled the water for 30 minutes prior to adding anything.

Discuss.

david_42 01-29-2007 06:07 PM

I expect #3 to produce the longest lag time and #1 the lowest gravity at 24 hours. I might be wrong, but more oxygen should mean more cell growth and less oxygen an earlier switch to alcohol production.

I probably would have added the yeast & stirred a little before splitting the batch up. On the other hand, I chose a Schwarzbier recipe for a lager/ale experiment & the carafal III dominates the flavor in both.

Bobby_M 01-29-2007 07:18 PM

I was concerned with unbalanced yeast cell addition but I stirred the hydrated yeast really well and measured the liquid additions very carefully. If any fermenter got more or less yeast, it couldn't be by too much. I'm guessing the variance could easily occur stirred into the wort as well.

I'm yet to analyze the entire time lapse, but I can say that #2 showed signs of offgassing first.

boo boo 01-29-2007 10:18 PM

I recently got an o2 system ( 5 micron airstone, filter, o2 regulator and hosing) and aerated my wort this past brewday using it. I pitched my usual amount of yeast and my temps are consistant with my previous brews (ambient 62f). I got action 12 hours after pitching vs 36 hours usual when using dry yeast sprinkled onto wort.
That was enough of an endorsement for me.

bandt9299 01-30-2007 02:10 AM

Can't wait to see the results, I've had bad luck so far with my O2 system, both brews stopped short in the .020's. Never had this happen until now, tommorrow I'm making a murphy's clone, almost the same as the Guinness I did 2 weeks ago (which started @ 1.042 and stopped @ 1.024 used O2 and airstone) but will use my old method of rack and splash, no O2 aeration, well see.

clayof2day 01-30-2007 01:56 PM

Quote:

Originally Posted by boo boo
vs 36 hours usual when using dry yeast sprinkled onto wort.

You should ALWAYS rehydrate dry yeast in boiled/cooled tap water. Rehydrating in wort, which contains high levels of sugars, sends the yeast into osmotic shock and you only recover about 30% of the viable yeast you would if you rehydrate in water before pitching.

Orfy 01-30-2007 02:04 PM

12 hours is typical for my brews using a rehydrated dried yeast. I've never had more than a 24hr lag even with sprinkling the yeast on dry.

If you want to add wort then add it a little at a time.

http://consumer.lallemand.com/dansta...starrehyd.html

Bobby_M 01-30-2007 03:03 PM

I spent some time creating the timelapse video and I'm going to share it here. Keep in mind though that I believe the real result most of you would be interested in is the gravity of each at the 48 hour mark. That time is coming up later this evening.


Orfy 01-30-2007 03:05 PM

Nice porn music. :rockin:
Good work, it seams not much between 2 & 3. The real test will come with the hydrometer. Number one is obviously gentler but that is no bad thing. It's not failed and it is going well.
If you look, there's less gunk on the foam of #1

Can't wait for the money shot.:D


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